Magnetic sensor sensitivity matching calibration

ABSTRACT

A magnetic sensor device comprises a substrate. A first magnetic sensor, a second magnetic sensor, and one or more inductors are disposed over the substrate and are controlled by a magnetic sensor controller having a control circuit. The control circuit is adapted for controlling the first magnetic sensor to measure magnetic fields under presence of a first set of magnetic fields, and for controlling the second magnetic sensor to measure magnetic fields under presence of a second set of magnetic fields generated by the inductors. The control circuit calculates a relative sensitivity matching value that converts magnetic field values measured by the second magnetic sensor to a comparable magnetic field value measured by the first magnetic sensor or vice versa. The control circuit is further adapted for correcting a measurement by the second magnetic sensor using the relative sensitivity matching value to produce a corrected measurement, and for calculating a magnetic field gradient by combining a measurement by the first magnetic sensor with the corrected measurement.

FIELD OF THE INVENTION

The present invention relates to integrated magnetic sensor calibration.

BACKGROUND OF THE INVENTION

Sensors are widely used in electronic devices to measure attributes ofthe environment and report a measured sensor value. In particular,magnetic sensors are used to measure magnetic fields, for example intransportation systems such as automobiles or in portable electronicdevices. Magnetic sensors can incorporate Hall effect sensors thatgenerate an output voltage proportional to an applied magnetic field ormagneto-resistive materials whose electrical resistance changes inresponse to an external magnetic field. Magneto-inductive and fluxgatemagnetic sensors are also used. For example, U.S. Pat. No. 6,545,462describes a sensor for the detection of the direction of a magneticfield having magnetic flux concentrators and Hall elements. The Hallelements are arranged in the area of the edge of the magnetic fieldconcentrator.

Other magnetic systems are integrated with an electrically conductivecoil, for example a wire wrapped in a helix forming a solenoid. Byapplying an electrical current to the solenoid, a magnetic field isformed that can be detected by a magnetic sensor. Various solenoids canhave different materials within the helix, for example an air core or aferromagnetic core such as iron. Other designs use magnets to provide afield.

U.S. Pat. No. 5,831,431 illustrates a miniaturized coil arrangement forthe detection of magnetically permeable materials. In this design, acore is provided in or parallel to a plane of the substrate and a coilwound around a section of the core so that at least a portion of thecoil extends out of the substrate plane. In contrast, U.S. Pat. No.6,404,192 discloses an integrated planar magnetic sensor with anexcitation coil formed in a planar winding made using integrated circuittechniques on a semiconductor substrate. Flat detection coils areprovided in different arrangements. U.S. Patent Publication No.2015/0316638 also describes a planar coil. WO2006067100 describes amagneto-resistive sensor with a modulation magnetic field.

EP1407945 describes a magnetic sensor system with a magnetic sensor andtwo magnets that provide a magnetic field to the sensor to overcomestray external magnetic fields.

Measurements from magnetic sensors can drift over time, providingvarying sensor measurements even when exposed to the same magneticfield. For example, the magnetic field measurements can be offset from adesired nominal value, the sensitivity can vary so that measurements area multiple (either greater or less than one) of the desired value, orboth. These changes in magnetic sensor response can have a variety ofcauses, including changes in environmental operating conditions such astemperature or humidity, changes in the magnetic sensor materialsincluding magnetically permeable materials due to aging, parasiticeffects such as ambient temperature variation, or mechanical stress onthe magnetic sensor or a package in which the magnetic sensor ismounted. It is important, therefore, to calibrate a magnetic sensor toprovide accurate measurement results when the magnetic sensor is firstput into use and also during operation, for example periodically or whenthe magnetic sensor is turned on and used. Furthermore, stray externalambient magnetic fields can be present during calibration or inoperation, complicating the process of accurately measuring a desiredmagnetic field. Moreover, due to manufacturing process and materialsvariation, as well as materials and operational aging, differentmagnetic sensors can have different performances and sensitivities tomagnetic fields so that measurements of identical magnetic fields canresult in different measured values.

Thus, in general and prior to their use, magnetic sensors are calibratedso as to eliminate or at least reduce any imprecision, measurementinaccuracy, or disturbances such as process dispersions duringmanufacture, magnetic interference caused by the circuitry that controlsthe magnetic sensor, interference due to external causes (e.g.,loudspeakers, batteries, ferromagnetic elements), and dependence upontemperature or time. Calibration generally consists in selecting anappropriate set of gain and offset values for each detection axis of amagnetometer, such as a tri-axis position sensor. The calibrationmethods are typically carried out at manufacture or else at installationof the device in an apparatus in which it is to be used (for example, inthe navigation system of an automobile).

Various magnetic sensor calibration methods are known and rely on thecalibration of the absolute sensitivity of the magnetic sensor, that is,the response of the magnetic sensor to an imposed external magneticfield, for example a magnetic field made by an integrated solenoid.Calibration can be accomplished using a continuous gain calibration loopsuch as an electronic amplifier whose gain is set to match a desiredvalue in response to the known external magnetic field. Some calibrationmethods rely on physically moving the sensors and making a set ofmeasurements to calibrate the device. For example, U.S. Pat. No.8,240,186 describes techniques for the calibration of magnetic sensorsby using one or more magnetic sensors to sample at least four datapoints taken as the sensors are rotated about an axis and performing amathematical operation to obtain offset values for the measured valuesand correcting the measured field values with the offset values tocalibrate the apparatus. The magnetic sensors can be spatially separatedand controlled by a controller. U.S. Pat. No. 7,835,879 finds multiplesolution sets and selects from among the solutions. U.S. Pat. No.8,825,426 uses motion during operation to make different magnetic fieldmeasurements and fits the measured data points to an ellipsoid tocalculate a magnetic field. U.S. Patent Application Publication No.2014033696 also employs an ellipsoidal model.

Another approach to providing sensor motion for calibration uses agenerated magnetic field, for example employing a magnet as described inU.S. Pat. No. 7,259,550 in which a magnetic calibration device includesat least one magnetic sensor, for example a Hall sensor, to becalibrated. At least one coil card is detachably attached and comprisesthree coils arranged substantially orthogonal to each other. A magnetgenerates a substantially homogeneous and constant calibration magneticfield and a rotator rotates the cards in the calibration magnetic fieldaround two substantially orthogonal axes. U.S. Patent ApplicationPublication No. 20090072815 describes a magnetic sensor device includingat least one magnetic excitation field generator for generating amagnetic excitation field and at least one magnetic calibration fieldgenerator for generating a magnetic calibration field. At least onemagnetic sensor element measures the magnetic reaction fields generatedby magnetic particles in reaction to the magnetic excitation fieldand/or the magnetic calibration field. The measurements are evaluated tocalibrate the magnetic sensor element.

Another magnetic sensor design incorporating magnetic-field-generatingcircuits is disclosed in U.S. Pat. No. 9,547,050 in which a sensorsystem carried by an electronic device is configured to detect anexternal magnetic field emitted by a magnetic source. The sensor systemcomprises a single substrate formed of non-magnetic material and havinga first surface and a second surface displaced from the first surface, afirst magnetic sensor at the first surface and a second magnetic sensorat the second surface, both detecting the external magnetic field atdifferent locations. The first magnetic sensor and the second magneticsensor concurrently (i) detect the external magnetic field and (ii)provide a first detection signal and a second detection signal,respectively. The first detection signal corresponds to a first magneticfield strength and the second detection signal corresponds to a secondmagnetic field strength. A processing circuit is coupled to the firstmagnetic sensor and the second magnetic sensor. The processing circuituses a difference between the first detection signal and the seconddetection signal to provide a direction of the external magnetic field.

U.S. Pat. No. 8,089,276 discloses a magnetic field sensor assembly withat least one magnetic field sensor integrated into a semiconductor chipand has at least one magnetic field source. The semiconductor chip andthe at least one magnetic field source are arranged relative to eachother in such a way that a magnetic field generated by the magneticfield source is detectable with the aid of at least one magnetic fieldsensor.

U.S. Pat. No. 8,669,761 describes a sensor circuit configured andoperated in the presence of interference. In connection with variousexample embodiments, a stray magnetic field is sensed with currentsensors that also respectively sense current-induced magnetic fieldsgenerated by current flowing in opposing directions through differentportions of a conductor. The current-induced magnetic fields and thestray magnetic field are coplanar, and the current sensors are arrangedsuch that a portion of the output from each current sensor correspondingto the stray magnetic field is canceled when the sensor outputs arecombined.

These magnetic sensors are typically calibrated using absolutesensitivity so that they simply correct for a measured bias, for exampleusing integrated coils and a continuous gain calibration loop and asdescribed in the above references. However, this method has drawbacksthat limit effectiveness, for example the magnetic field from integratedcoils is relatively low, inhibiting the magnetic sensor's ability toovercome external stray magnetic fields, and the calibration is only asaccurate as the current source used to generate the current passedthrough the integrated solenoid coil. These drawbacks lead to inaccuratemagnetic sensor calibration.

There is an ongoing need, therefore, for effective calibration methodsand structures for magnetic sensors operable under a wide range ofmeasurement conditions for detecting a wide range of magnetic fields indifferent locations.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a magnetic sensor deviceincluding a substrate having a surface, a first magnetic sensor A fordetecting a magnetic field disposed at a first location on, over, or indirect contact with the surface, a second magnetic sensor B fordetecting a magnetic field disposed at a second location different fromthe first location on, over, or in direct contact with the surface, andone or more inductors disposed over the substrate surface and located toprovide a magnetic field to the first magnetic sensor A and to thesecond magnetic sensor B. A magnetic sensor controller has a controlcircuit for controlling the first magnetic sensor A, the second magneticsensor B, and the one or more inductors. The control circuit includescircuitry adapted for controlling one or more inductors to provide afirst set of magnetic fields to the first sensor and a second set ofmagnetic fields to the second sensor. The control circuit calculates arelative sensitivity matching value S that converts magnetic fieldvalues measured by the first magnetic sensor A when the first set ofmagnetic fields is applied to comparable magnetic field values measuredby the second magnetic sensor B when the second set of magnetic fieldsis applied or converts magnetic field values measured by the secondmagnetic sensor B when the second set of magnetic fields is applied to acomparable magnetic field value measured by the first magnetic sensor Awhen the first set of magnetic fields is applied. The control circuit isadapted for correcting a measurement by the second magnetic sensor usingthe relative sensitivity matching value to produce a correctedmeasurement, and for calculating a magnetic field gradient by combininga measurement by the first magnetic sensor and the correctedmeasurement. In particular embodiments of the present invention, theinvention not being limited thereto, the control circuit may forinstance calculate a ratio of difference values between magnetic fieldsmeasured by the first magnetic sensor A and magnetic fields measured bythe second magnetic sensor B, i.e. the value ((A1−A2)/(B1−B2)), toproduce the relative sensitivity matching value S. In an embodiment, theinductor is a magnetic field source, a coil, a solenoid, or a straightconductor.

In an embodiment, the control circuit includes circuitry that cancontrol the first magnetic sensor A to measure the ambient magneticfield, control the second magnetic sensor B to measure the ambientmagnetic field, and combine the two measurements to form a magneticfield measurement. The control circuit can control the one or moreinductors to provide at least one magnetic field of the first set or atleast one magnetic field of the second set to be zero (no magneticfield) during the measurements or can control the one or more inductorsto provide a magnetic field during the measurements. The control circuitcan, but does not have to, control the first magnetic sensor A tomeasure the ambient magnetic field at the same time that the controlcircuit controls the second magnetic sensor B to measure the ambientmagnetic field.

In another embodiment, the control circuit includes circuitry thatcontrols the one or more inductors to provide a magnetic field having aforward polarity and controls the first magnetic sensor A to measure theambient magnetic field including the forward polarity magnetic field,controls the one or more inductors to provide a magnetic field having areverse polarity and controls the first magnetic sensor A to measure theambient magnetic field including the reverse polarity magnetic field,and then calculates the ambient magnetic field excluding any fieldprovided by the one or more inductors by combining the two measurements,for example computing a difference or sum between the two measurements.Alternatively, the control circuit includes circuitry that controls theone or more inductors to provide a magnetic field having a forwardpolarity and controls the first magnetic sensor A to measure the ambientmagnetic field including the forward polarity magnetic field, controlsthe one or more inductors to provide a magnetic field having a reversepolarity and controls the second magnetic sensor B to measure theambient magnetic field including the reverse polarity magnetic field,corrects the measurement by the second magnetic sensor B using therelative sensitivity matching value S to produce a correctedmeasurement, and then calculates the ambient magnetic field excludingany field provided by the one or more inductors by combining themeasurement by the first magnetic sensor A and the corrected measurementderived from the second magnetic sensor B measurement, for examplecomputing a difference or sum between the first magnetic sensor Ameasurement and the corrected measurement.

In one configuration, the control circuit controls the first magneticsensor A to measure the ambient magnetic field and controls the secondmagnetic sensor B to measure the ambient magnetic field, possibly at thesame time, and calculates a magnetic field gradient by correcting one ofthe measured values and combining the corrected value with the othermeasured value. The control circuit can control the one or moreinductors to provide no magnetic field during the measurements or cancontrol the one or more inductors to provide a magnetic field during themeasurements.

In an embodiment, the relative sensitivity matching value S includes oris a multiplication or division factor, the relative sensitivitymatching value S includes or is an additive or subtractive offsetfactor, or the relative sensitivity matching value S includes both amultiplication or division factor and an additive or subtractive offsetfactor.

A method of matching multiple magnetic sensors in a magnetic sensordevice includes providing (i) a substrate having a surface, (ii) a firstmagnetic sensor A disposed at a first location on, over, or in directcontact with the surface, (iii) a second magnetic sensor B disposed at asecond location on, over, or in direct contact with the surface, themagnetic sensor A and the magnetic sensor B both detecting a magneticfield, and the first location different from the second location, (iv)one or more inductors disposed over the substrate surface and located toprovide a magnetic field to the first magnetic sensor A and a magneticfield to the second magnetic sensor B, and (v) a magnetic sensorcontroller having a control circuit including circuitry for controllingthe first magnetic sensor A, the second magnetic sensor B, and the oneor more inductors. The method includes controlling the one or moreinductors to provide a first set of magnetic fields and controlling thefirst magnetic sensor to measure these magnetic fields; and controllingthe one or more inductors to provide a second set of magnetic fields andcontrolling the second magnetic sensor to measure these magnetic fields.The control circuit calculates a relative sensitivity matching value Sthat converts magnetic field values measured by the first magneticsensor A to a comparable magnetic field value measured by the secondmagnetic sensor B or converts magnetic field values measured by thesecond magnetic sensor B to a comparable magnetic field value measuredby the first magnetic sensor A. The method further includes correcting ameasurement by the second magnetic sensor using the relative sensitivitymatching value to produce a corrected measurement, and calculating amagnetic field gradient by combining a measurement by the first magneticsensor and the corrected measurement. In particular embodiments of thepresent invention, the control circuit may for instance calculate aratio of difference values between magnetic fields measured by the firstmagnetic sensor A and magnetic fields measured by the second magneticsensor B, i.e. the value ((A1−A2)/(B1−B2)), to produce the relativesensitivity matching value S.

In embodiments, the first magnetic sensor A is controlled by the controlcircuit to measure the ambient magnetic field, the second magneticsensor B is controlled by the control circuit to measure the ambientmagnetic field, and the control circuit corrects the measurement byeither the first or second magnetic sensors A, B and combines thecorrected measurement and the uncorrected measurement to form a magneticfield measurement. The one or more inductors can be controlled by thecontrol circuit to provide no magnetic field during the measurements orcontrolled by the control circuit to provide a magnetic field during themeasurements.

The first magnetic sensor A can be controlled by the control circuit tomeasure the ambient magnetic field and the second magnetic sensor B canbe controlled by the control circuit to measure the ambient magneticfield at the same time.

In another method, the control circuit controls the one or moreinductors to provide a magnetic field having a forward polarity and thefirst magnetic sensor A to measure the ambient magnetic field includingthe forward polarity magnetic field, controls the one or more inductorsto provide a magnetic field having a reverse polarity and the firstmagnetic sensor A to measure the ambient magnetic field including thereverse polarity magnetic field, and then calculates the ambientmagnetic field excluding any field provided by the one or more inductorsby combining the two measurements, for example computing a sum ordifference between the two measurements.

Alternatively, the control circuit controls the one or more inductors toprovide a magnetic field having a forward polarity and the firstmagnetic sensor A to measure the ambient magnetic field including theforward polarity magnetic field, controls the one or more inductors toprovide a magnetic field having a reverse polarity and the firstmagnetic sensor B to measure the ambient magnetic field including thereverse polarity magnetic field, corrects the measurement by the secondmagnetic sensor B using the relative sensitivity matching value S toproduce a corrected measurement, and then calculates the ambientmagnetic field excluding any field provided by the one or more inductorsby combining the measurement by the first magnetic sensor A and thecorrected measurement, for example by adding or subtracting themeasurements.

In some embodiments of the present invention, the control circuit

controls the first magnetic sensor A to measure a first magnetic fieldA1 and the one or more inductors to provide a fifth magnetic field,

controls the first magnetic sensor A to measure a third magnetic fieldA2 and the one or more inductors to provide a sixth magnetic field,

controls the second magnetic sensor B to measure a second magnetic fieldB1 and the one or more inductors to provide the fifth magnetic field,and

controls the second magnetic sensor B to measure a fourth magnetic fieldB2 and the one or more inductors to provide the sixth magnetic field. Insome embodiments, the fifth magnetic field is zero. In otherembodiments, the fifth and sixth magnetic fields have oppositedirections or have a common magnitude.

In another method, the control circuit controls the first magneticsensor A to measure the ambient magnetic field, controls the secondmagnetic sensor B to measure the ambient magnetic field, possibly at thesame time, and calculates a magnetic field gradient by correcting one ofthe measurements and combining the corrected measurement with theuncorrected measurement. In an embodiment, the control circuit controlsthe one or more inductors to provide no magnetic field during themeasurements or to provide a magnetic field during the measurements.

In various methods, the relative sensitivity matching value S iscalculated to include or is a multiplication or division factor, therelative sensitivity matching value S is calculated to include or is anadditive or subtractive offset factor, or the relative sensitivitymatching value S is calculated to include both a multiplication ordivision factor and an additive or subtractive offset factor.

The substrate can include an electronic circuit that controls themagnetic sensors A, B, the one or more inductors, or both. Theelectronic circuit can operate the magnetic sensors A, B to measure amagnetic field and can operate the one or more inductors to provide atest magnetic field. The electronic circuit can also include acalculation circuit that calculates correction or calibration factorsfor magnetic field measurements.

The circuit can provide current to all of the one or more inductors atthe same time or to less than all of the one or more inductors at thesame time. The circuit can provide current to inductors on oppositesides of the magnetic sensor and not to others of the inductors at thesame time. The circuit can sequentially provide power to one or a groupof inductors and subsequently provide current to another one or group ofinductors to enable measurements of magnetic fields having field lineswith different directions.

The one or more inductors can provide a magnetic field at the magneticsensor location greater than or equal to 1 mT, 3 mT, 5 mT, 10 mT, 15 mT,20 mT, or 50 mT.

Embodiments of the present invention provide effective calibrationmethods and structures for magnetic sensors operable under a wide rangeof measurement conditions for detecting a wide range of magnetic fieldsin different locations.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects, features, and advantages ofthe present disclosure will become more apparent and better understoodby referring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a plan view of an embodiment of the present invention having asingle inductor;

FIGS. 2A and 2B are a detail perspective view and cross-sectional view,respectively, of an inductor structure according to an embodiment of thepresent invention;

FIG. 3 is a perspective view of an embodiment of the present inventioncorresponding to FIG. 1;

FIG. 4A is a plan view of an alternative embodiment of the presentinvention having multiple inductors;

FIG. 4B is a plan view of an alternative embodiment of the presentinvention having multiple inductors that form magnetic fields indifferent directions;

FIG. 4C is a perspective view of an embodiment of the present inventionhaving two inductors in different planes;

FIG. 4D is a perspective view of an embodiment of the present inventiontwo inductors in different planes, of which one is a planar coil;

FIG. 5A is a perspective view of an embodiment of the present inventioncorresponding to FIG. 4A;

FIG. 5B is a perspective view of an embodiment of the present inventionhaving three inductors;

FIGS. 6-10 are flow diagrams illustrating various methods of embodimentsof the present invention; and

FIG. 11 is a perspective view of an inductor having wire-bond wiresaccording to an embodiment of the present invention.

The features and advantages of the present disclosure will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements. In the drawings, like reference numbersgenerally indicate identical, functionally similar, and/or structurallysimilar elements. The figures are not drawn to scale since the variationin size of various elements in the Figures is too great to permitdepiction to scale. The dimensions and relative dimensions do notnecessarily correspond to actual reduction to practice of the invention.The drawings are only schematic, and they are not intended to belimiting. Also reference signs in the claims shall not be construed aslimiting the scope.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of the present invention provide effective calibrationmethods and structures for magnetic sensors operable under a wide rangeof measurement conditions for detecting a wide range of magnetic fieldsin different locations in a reduced form factor and with improvedmanufacturability. Referring to the plan view of FIG. 1 and theperspective view of FIG. 3, a magnetic sensor device 99 comprises asubstrate 10 having a surface. A first magnetic sensor A for detecting amagnetic field is disposed at a first location on, over, or in directcontact with the substrate 10 surface. A second magnetic sensor B fordetecting the same or a different magnetic field is disposed at a secondlocation on, over, or in direct contact with the substrate 10 surface.For example, the first or second magnetic sensor A or B can be disposedon a dielectric layer 12 that insulates the magnetic sensor A or B fromthe underlying substrate 10, for example a conductive or semiconductorsubstrate 10. The first location is different from the second location.The first and second magnetic sensors A, B are collectively referred toherein as magnetic sensors 30.

One or more inductors 20 are disposed over the substrate 10 surface andlocated to provide a magnetic field to the first magnetic sensor A atthe first location and a magnetic field to the second magnetic sensor Bat the second location. In an embodiment, the magnetic field at thefirst location has the same strength and/or field orientation as themagnetic field at the second location. In another embodiment, themagnetic field at the first location has a different strength and/orfield orientation as the magnetic field at the second location. In anembodiment, the inductor 20 is a magnetic field source, a coil, asolenoid, or a straight conductor. Both the coil and the solenoid arehelically wound conductors. The straight conductor is a straight wirethrough which a current passes to create a magnetic field.

A magnetic sensor controller 40 has a control circuit 42 that includescircuitry for controlling the first magnetic sensor A, the secondmagnetic sensor B, and the one or more inductors 20. In oneconfiguration of the magnetic sensor device 99, the magnetic sensorcontroller 40, the first magnetic sensor A, or the second magneticsensor B is a packaged integrated circuit. In another configuration, themagnetic sensor controller 40, the first magnetic sensor A, or thesecond magnetic sensor B is a surface mount device or a bare integratedcircuit die, for example micro-transfer printed to the substrate 10surface. Alternatively, one or more of the magnetic sensor controller40, the first magnetic sensor A, or the second magnetic sensor B isformed in or on the substrate 10 surface and is native to the substrate10. The substrate 10 can be a semiconductor substrate, for example witha dielectric layer 12 disposed on the semiconductor substrate 10.

By controlling the electrical current through the coil 25 formed by theinductor 20 (see FIG. 2A), the control circuit 42 forms a magnetic fieldthat is detected by the magnetic sensors 30. The magnetic sensors 30 candetect the magnetic field or changes in the magnetic field, for exampledue to externally generated magnetic fields or the presence ofmagnetically sensitive materials, such as ferromagnetic materials.

In one embodiment, the magnetic sensor device 99 comprises a pluralityof inductors 20 and coils 25 and the control circuit 42 provides currentto all of the inductors 20 at the same time. In another embodiment, themagnetic sensor device 99 comprises a plurality of inductors 20 and thecontrol circuit 42 provides current to less than all of the inductors 20at the same time. In yet another embodiment, the magnetic sensor device99 comprises a plurality of inductors 20 and the control circuit 42provides current to only some and not all of the inductors 20 at thesame time. In a further embodiment, the magnetic sensor device 99comprises a plurality of inductors 20 and the control circuit 42provides current to a group of inductors 20 at the same time and thensubsequently provides current to a different group of inductors 20 atthe same time, for example to measure magnetic fields associated withmagnetic field lines having a direction or gradient.

In an embodiment of the present invention, the magnetic sensorcontroller 40 and control circuit 42 are electrically connected to thefirst magnetic sensor A, the second magnetic sensor B, and the one ormore inductors 20 through substrate conductors 16. The magnetic sensorcontroller 40 can be itself controlled by an external device, forexample an electronic system incorporated into an automobile, throughelectrical connections such as flex or ribbon cables to substrate 10contact pads 18 that are electrically connected to the control circuit42 through substrate conductors 16. The electrical substrate conductors16 can be patterned metal traces or wires, made using photolithographicor printed circuit techniques and materials on or in the substrate 10 orthe dielectric layer 12.

The control circuit 42 and magnetic sensor controller 40 can be anelectronic circuit, for example an analog electronic circuit, a digitalelectronic circuit, or a mixed-signal electronic circuit, and caninclude logic circuits for calculating or computing, a computer, statemachines, transistors, power transistors, and/or circuits for providingor receiving electronic signals including voltage or current signals.The control circuit 42 can comprise one or more digital or analogcomputing, calculating, or controlling devices or circuits either on thesubstrate 10 or external to the substrate 10, or both.

The first magnetic sensor A or the second magnetic sensor B can be anyone of a variety of suitable electrically operated magnetic sensors, forexample, a Hall sensor, a magneto-resistive sensor, a fluxgate sensor,or a magneto-inductive sensor and can be formed in, on or over thesubstrate 10 or disposed in, on, or over the substrate 10, for exampleby micro-transfer printing or using surface-mount techniques. Themagnetic sensors 30 can be provided in integrated circuits disposed onthe substrate 10 or in circuits formed or disposed on, in, or in directcontact with the substrate 10, a surface of the substrate 10, or a layeron the substrate 10, such as dielectric layer 12. The first magneticsensor A, the second magnetic sensor B, or the magnetic sensorcontroller 40 can be electrically connected with the substrateconductors 16.

According to embodiments of the present invention and referring to thedetailed perspective view of FIG. 2A and the corresponding cross sectionof FIG. 2B, an inductor 20 is a device that forms a magnetic field inresponse to an applied electrical current. The one or more inductors 20can comprise a coil electrical conductor 24 helically wrapped in a coil25 (a helix) around a core 22. The coil electrical conductor 24 can be ametal conductor (e.g., a metal wire, such as copper, aluminum, tungsten,silver, gold, titanium, tin, or other metals or metal alloys) or anymaterial that conducts electricity. The one or more inductors 20generate a magnetic field when provided with electrical current throughthe coil 25. The core 22 of each inductor 20 extends along the length ofeach inductor 20, where the length is the longest dimension of theinductor 20, or extends in the direction of a center line at the centerof each coil 25. The core 22 can be any of a variety of substances, forexample air (i.e., atmosphere) or a ferromagnetic material (e.g., iron).Because ferromagnetic materials can themselves conduct electricity, thecore 22 can be insulated from the electrically conductive coil 25 with acore insulator 26, as shown in the perspective view of FIG. 2A and thecross section of FIG. 2B. The core insulator 26 can be coated ordisposed over the core 22 (as shown). In another embodiment, the coreinsulator 26 is provided around the coil electrical conductors 24(wires) of the coil 25 (not shown), or only in the location of the coilelectrical conductors 24 over the core 22, and can include a portion ofan insulating dielectric layer 12 disposed over the substrate 10. Thecore insulator 26 can be any of a variety of insulators, for example aplastic, a resin, a cured polymer, an oxide such as silicon dioxide, ora nitride such as silicon nitride. The inductor 20 or core 22 can beadhered to a surface of the substrate 10 or embedded in a layer on thesubstrate 10, for example disposed or embedded in the dielectric layer12 or an adhesive provided on the substrate 10. The dielectric layer 12can be a polymer or other insulator such as silicon dioxide or a curedadhesive, such as SU8. The coil electrical conductors 24 can beconnected between the core 22 and the substrate 10 with an electricalsubstrate conductor 16, for example made using photolithographicprocesses and electrically conductive materials such as metal. Vias 17can be used to connect the coil electrical conductors 24 with thesubstrate conductors 16 if the dielectric layer 12 provides insulationto the core 22.

In an embodiment of the present invention, at each point where the coilelectrical conductors 24 of the coil 25 contact the substrate 10 or alayer (e.g., dielectric layer 12) on the substrate 10, a substratecontact pad 18 is disposed that forms an electric connection through avia 17 to the corresponding electrical substrate conductor 16 of thecoil 25 (FIG. 2B). Adjacent substrate contact pads 18 are electricallyconnected on opposing sides of the inductor 20 location with substrateconductors 16 to connect the coil electrical conductors 24 in a helicalcoil 25. Thus, electrical signals sent from the control circuit 42through a substrate conductor 16 to a first substrate contact pad 18pass through the first substrate contact pad 18 into a coil electricalconductor 24 of the coil 25, pass through a first coil electricalconductor 24 of the coil 25 over the core 22 to the other side of theinductor 20, enter a second substrate contact pad 18 and pass into asecond substrate conductor 16, pass under the inductor 20 into a thirdsubstrate contact pad 18, into a second coil electrical conductor 24 ofthe coil 25 and over the core 22, again, and so on, until the electricalsignal is returned through a substrate conductor 16 to the controlcircuit 42. As shown in FIG. 2B, the coil electrical conductor 24 (andthe core 22) is insulated from the substrate conductors 16 by thedielectric layer 12. Thus, the substrate contact pads 18 formed overvias 17 in the dielectric layer 12 enable electrical contact between thecoil electrical conductors 24 and the substrate conductors 16.

The substrate 10 can be one of many substrates with a surface capable ofsupporting or receiving the magnetic sensor 30 and one or more inductors20, for example a glass, plastic, ceramic, or semiconductor substratewith two opposing relatively planar and parallel sides. The substrate 10can have a variety of thicknesses, for example 10 micrometers to severalmillimeters. The substrate 10 can be a portion or surface of anotherdevice or integrated circuit and can include electronic circuitry.

According to embodiments of the present invention and referring also tothe flow diagram of FIG. 6, in operation a magnetic sensor device 99 isprovided in step 100. One or more inductors 20 are controlled to providea first set of magnetic fields to the first sensor A, and to provide asecond set of magnetic fields to the second sensor B. Each of the firstand second sets of magnetic fields comprise at least two magneticfields. As an example only, not limiting the present invention thereto,the first set of magnetic fields may comprise a fifth and a seventhmagnetic field, and the second set of magnetic fields may comprise asixth and an eighth magnetic field. This example is illustrated in FIG.6 and explained hereinafter in more detail. In step 110, the controlcircuit 42 controls the first magnetic sensor A to measure a firstmagnetic field A1 and the one or more inductors 20 to provide a fifthmagnetic field (a first magnetic field of the first set), for example no(zero) magnetic field. Before, after, or at the same time, in step 120,the control circuit 42 controls the second magnetic sensor B to measurea second magnetic field B1 and the one or more inductors 20 to provide asixth magnetic field (a first magnetic field of the second set), forexample also no magnetic field, or a magnetic field different from thefifth magnetic field. The measured first and second magnetic fields canbe, but do not have to be, the same magnetic field. In step 130, themagnetic field generated by the one or more inductors 20 is controlledby the magnetic sensor controller 40, to provide a seventh magneticfield (a second magnetic field of the first set) that can be differentfrom the fifth magnetic field. Either one of the fifth and seventhmagnetic fields may for instance be zero magnetic fields. The firstmagnetic sensor A is controlled in step 140 to measure a third magneticfield A2 under the magnetic influence of the inductor-induced seventhmagnetic field and, before, after, or at the same time, the secondmagnetic sensor B is controlled in step 150 to measure a fourth magneticfield B2 under the magnetic influence of an inductor-induced eighthmagnetic field (a second magnetic field of the second set). The measuredthird and fourth magnetic fields can be the same magnetic field, aforward-polarity magnetic field, or a reverse-polarity magnetic field.The polarity of the magnetic field provided by one inductor 20 can beopposite the polarity of the magnetic field of the other inductor 20(i.e. one inductor 20 can produce a forward-polarity magnetic field anda different inductor 20 can produce a reverse-polarity magnetic field)and can have a common magnitude. (The polarity of a magnetic fieldcorresponds to the direction of the field and opposing polarity fieldshave opposite directions.) Steps 140 and 150 can be done before (notshown) or after (as shown) steps 110 and 120, so long as the one or moreinductors 20 are controlled to produce a non-zero magnetic field,optionally different non-zero seventh and eighth magnetic fields, (forsteps 140, 150) or a different, potentially zero, magnetic field,optionally different fifth and sixth magnetic fields, (steps 110, 120)by turning the fifth, sixth, seventh and eighth magnetic fieldsgenerated by the one or more inductors on (step 130) or off (step 170),as appropriate, and controlling them appropriately. In one efficientmethod, steps 110 and 120 are done at the same time and steps 140 and150 are done at the same to reduce the number of times the magneticfields generated by the one or more inductors 20 are turned on or off.The controlling of the fifth, sixth, seventh and eighth magnetic fieldsseparately allows providing different calibration fields to the secondsensor compared to the first sensor.

After the first to fourth magnetic field measurements A1, A2, B1, B2 aremade, the control circuit 42 of the magnetic sensor controller 40 cancalculate a value (for instance, but not limited thereto,(A1−A2)/(B1−B2)) in step 160 that is, provides, or contributes to arelative sensitivity matching value S. The value S can be a relativesensitivity matching value that converts first and third magnetic fieldvalues measured by the first magnetic sensor A to comparable second andfourth magnetic field values measured by the second magnetic sensor B orconverts second and fourth magnetic field values measured by the secondmagnetic sensor B to comparable first and third magnetic field valuesmeasured by the first magnetic sensor A. Two comparable values can bedirectly compared without requiring a functional conversion, for exampleby finding a difference, a sum, or an average of the two comparablevalues. Optionally, the sixth magnetic field generated by the inductor20 is turned off in step 170, after or before the calculation of step160.

The magnetic sensors A and B can be calibrated to compensate for a knownsusceptibility to environmental influences that are present during themeasurements or have a pre-determined or systematic difference that canalso be corrected by a calibration. Thus, the measurements of the firstto fourth magnetic fields A1, A2, B1, B2 can be corrected in response toknown calibration parameters, either at all times, or in response totransient or environmental factors.

In general, a magnetic sensor 30 will detect a magnetic field from thesensor itself and any external, stray magnetic fields induced by theenvironment. If an inductor also produces a magnetic field, then themagnetic sensor will respond to the sum of these fields,B=B_(M)+B_(E)+B_(S), where B_(M) is the sensor magnetic field, BE is theexternal, stray magnetic field, and B_(S) is the field due to theinductor coil 25. Different sensors (e.g., first and second magneticsensors A, B) will also have different sensitivities (responses) to amagnetic field due to differences in materials and the manufacturingprocess. According to embodiments of the present invention, thesedifferences can be discounted by calculating:

$\left( {\left( {{A\; 1} - {A\; 2}} \right)\text{/}\left( {{B\; 1} - {B\; 2}} \right)} \right) = {\left( \frac{{A\; 1} - {A\; 2}}{{B\; 1} - {B\; 2}} \right) = \left( \frac{\left( {{A\; 1M} + {A\; 1E}} \right) - \left( {{A\; 2M} + {A\; 2E} + {A\; 2S}} \right)}{\left( {{B\; 1M} + {B\; 1E}} \right) - \left( {{B\; 2M} + {B\; 2E} + {B\; 2S}} \right)} \right)}$

Since the first magnetic field A1 and the third magnetic field A2 aredifferent measurements made by the same first magnetic sensor A so thatA1_(M)=A2_(M), since the second magnetic field B1 and the fourthmagnetic field B2 are different measurements made by the same secondmagnetic sensor B so that B1_(M)=B2_(M), and assuming that the externalstray magnetic field does not change between the first and secondmeasurements so that A1_(E)=A2_(E) and B1_(E)=B2_(E) then the equationreduces to

${\left( \frac{A\; 2S}{B\; 2S} \right) = \left( {A\; 2_{S}\text{/}B\; 2_{S}} \right)},$

which is, provides, or contributes to the relative sensitivity S of themagnetic sensor A with respect to the magnetic sensor B.

In other embodiments, the relative sensitivity matching value S is orincludes an additive or subtractive offset value, for example determinedat the time of magnetic sensor device 99 production. Thus, in a furtherembodiment, S=k*c−f, where S is the corrected measurement (in Gauss, forexample), k is the sensitivity, c is the measurement value (expressed inVolts, for example), and f is an offset. K, c and f are calculated ormeasured constants and c can for instance equal ((A1−A2)/(B1−B2)). Theoffset value f can be dependent on the current provided through theelectrical conductors 24 of the coil 25 of the inductor 20. Inconsequence, embodiments of the present invention can operate even ifdifferent electrical currents are provided for different measurementsfor the magnetic sensors A, B. In various embodiments, the relativesensitivity matching value S includes or is a multiplication or divisionfactor, the relative sensitivity matching value S includes or is anadditive or subtractive offset factor, or the relative sensitivitymatching value S includes both a multiplication or division factor andan additive or subtractive offset factor. In general, the relativesensitivity matching value S is a transformation value, function,algorithm, or operation that corrects (converts or matches) measurementsmade by one magnetic sensor 30 to corrected measurements that arecomparable to measurements made by another magnetic sensor. Althoughshown in some embodiments herein as the equation ((A1−A2)/(B1−B2)) andused as to correct measurements by multiplication, the relativesensitivity matching value S is not limited to that equation and thecorrection function is not limited to a product. The relativesensitivity matching value S and correction function can incorporateother factors or functions such as linear equations, algorithms, orother additive, subtractive, multiplicative, or divisive constants ormathematical transformations.

Note that it is not essential that the magnetic field produced by theone or more inductors 20 is the same at the first and second locationsof the corresponding first magnetic sensor A and second magnetic sensorB, since any differences will be included in the relative sensitivitymatching value S. The relative sensitivity matching value S can then beapplied to any magnetic field value measured by the second magneticsensor B to a comparable value measured by the first magnetic sensor Aor vice versa by calculating or otherwise converting the measuredmagnetic field value appropriately using the relative sensitivitymatching value S.

Referring to FIG. 7, for example, with or without the magnetic fieldproduced by the one or more inductors 20 under the control of themagnetic sensor controller 40 (e.g., optional step 131), first andsecond ambient magnetic fields A3 and B3 can be measured in steps 180and 190 by first magnetic sensor A and second magnetic sensor B. In anembodiment, the measurements are done at the same time but, in otherembodiments, they can be done at different times. One of the measuredfirst and second ambient magnetic fields A3 or B3 is converted in step200 using the relative sensitivity matching value S to provide acorrected ambient magnetic field value B3′ (as illustrated, or A3′ (notillustrated)) and combined in step 210 with the other of the measuredfirst and second ambient magnetic fields A3 or B3 to produce a finalmeasured ambient magnetic field value that is indifferent to differencesin first magnetic sensor A and second magnetic sensor B or to strayexternal fields, as long as the stray external magnetic fields areconstant or consistent between the first magnetic sensor A and secondmagnetic sensor B. Since the calibration steps of FIG. 6 can be repeatedas often as necessary after manufacturing or in operation, the relativesensitivity matching value S can adapt to a variety of factors includingchanges in environment (e.g., temperature or humidity), changes indevice materials or structure due to aging or operation, or changes inexternal stray magnetic fields.

As shown in FIGS. 1 and 3, embodiments of the present invention caninclude only a single inductor 20. In general, however, variousembodiments of the present invention can include multiple magneticsensors 30 sharing a common inductor 20 (as in FIGS. 1 and 3), multiplemagnetic sensors 30 each having a corresponding associated individualinductor 20 (as in FIGS. 4A, 4B, 4C, 4D and 5A, 5B), or multiplemagnetic sensors 30 and shared or individual multiple inductors 20.

Referring to the plan view of FIG. 4A and the corresponding perspectiveview of FIG. 5A, a magnetic sensor device 99 in an embodiment of thepresent invention includes two inductors 20, each arranged to provide amagnetic field to a corresponding associated magnetic sensor 30 (e.g.,first magnetic sensor A and second magnetic sensor B) disposed on asubstrate 10 or dielectric layer 12. The inductors 20 can beelectrically connected in series (as shown) with substrate conductors 16so that an identical electrical current passes through each inductor 20in response to the magnetic sensor controller 40 control circuit 42.Alternatively, the inductors 20 can be electrically connected inparallel (not shown) and the same or different electrical currents canbe passed through the different inductors 20. The inductors 20 can besimilar and produce similar magnetic fields or can be different andproduce different magnetic fields. The magnetic sensors 30 can belocated in a similar location or direction with respect to acorresponding associated inductor 20 or in a different location ordirection, as shown in FIG. 4B. In one embodiment, the inductors 20 formmagnetic fields in orthogonal directions in a common plane (FIG. 4B, forexample when the centerlines of the inductors 20 are in a common plane)and in other embodiments, as shown in FIGS. 4C and 4D, the inductors 20form magnetic fields in orthogonal directions in different planes, forexample when the centerlines of the inductors 20 are not in a commonplane. Such structures can be formed when the centerlines of differentinductors 20 are, for example, in the x, y, or z directions and can beperpendicular to each other in any arrangement or combination. In someconfigurations of the present invention, as for instance illustrated inFIG. 4D, inductors 20 can be planar coils integrated on a surface or ina plane on or over a substrate 10 or a dielectric layer 12, for exampleon an integrated circuit. In these cases any combination of the magneticfields Bx, By, and Bz present can be orthogonal to each other in oneplane or in different planes. FIG. 4B also illustrates embodiments inwhich the magnetic field provided by two different inductors 20 aresensed by a common magnetic sensor 30 (magnetic sensor B). In general,any magnetic sensor 30 can sense the magnetic field of one or moreinductors 20 and the magnetic field produced by an inductor 20 can besensed by one or more magnetic sensors 30 (e.g., as in FIG. 3). Any suchdifferences can be accommodated by the relative sensitivity matchingvalue S and the response of one magnetic sensor 30 can be converted to acomparable response for another magnetic sensor 30.

In various methods and embodiments of the present invention, referringto the flow diagram of FIG. 8, measurements made by one sensor (e.g.,first magnetic sensor A) can be corrected or converted to be comparableto measurements made by another sensor (e.g., second magnetic sensor B)using the relative sensitivity matching value S. In step 250, the secondmagnetic field measurement B1 (made with the sixth inductor-inducedmagnetic field, e.g. without an inductor-induced magnetic field) isconverted to value B 1′ and combined with the first magnetic fieldmeasurement A1 in step 270. Similarly, in step 260, the fourth magneticfield measurement B2 (made with the eighth inductor-induced magneticfield different from the sixth inductor-induced magnetic field, e.g.with a non-zero inductor-induced magnetic field) is converted to valueB2′ and combined with the third magnetic field measurement A2 in step280. The combined values can themselves be used to calculate, compare,or derive magnetic field values in step 290. The steps are illustratedin FIG. 8 with dashed lines denoting that they are optional steps thatcan be used for some magnetic field calculations and not in othercalculations, or that different measured magnetic field values can becombined or compared to find useful magnetic field values.

The inductors 20 in the plurality of inductors 20 can be electricallyconnected in common, for example in series or in parallel, and operateat the same time in response to the same signal. In such an embodiment,the inductors 20 in the plurality of inductors 20 can also be consideredas a single inductor 20 with multiple cores 22. Alternatively, eachinductor 20 in the plurality of inductors 20 can be electricallyseparate and controlled separately from any of the other inductors 20with separate electrical control signals, for example provided by thecontrol circuit 42. In yet another embodiment, inductors 20 in differentgroups of inductors 20 in the plurality of inductors 20 are electricallyconnected in common, for example in series or in parallel, and thegroups of inductors 20 are electrically separate and controlledseparately from any of the other inductors 20 with separate electricalcontrol signals.

In another embodiment of the present invention, referring to FIG. 9,electrical current through the inductors 20 is controlled by themagnetic sensor controller 40 in a forward and in a reverse polarity,where the reverse polarity reverses the voltage across the terminals ofthe inductor 20 to send current through the inductor 20 in a reversedirection and form a magnetic field with reversed polarity. In step 300,the magnetic sensor controller 40 applies current to the coil(s) 25 ofthe one or more inductors 20 to form a magnetic field with a forward(positive) polarity. Seventh magnetic field A4 is measured by the firstmagnetic sensor A in step 310 and eighth magnetic field B4 is measuredby the second magnetic sensor B in step 320. The magnetic sensorcontroller 40 then applies current to the coil(s) 25 of the one or moreinductors 20 to form a magnetic field with a reverse (negative) polarityin step 330. Ninth magnetic field A5 is measured by the first magneticsensor A in step 340 and tenth magnetic field B5 is measured by thesecond magnetic sensor B in step 350. The measurements of the seventhand ninth magnetic fields A4 and A5 are optionally combined in step 360and the measurements of the eighth and tenth magnetic fields B4 and B5are optionally combined in step 370. Thus, the magnetic sensorcontroller 40 can compute or calculate the ambient magnetic fieldexcluding any field provided by the one or more inductors 20 bycomputing a sum or difference between the two measurements. Such amethod also provides a signal having double the absolute magnitude,possibly reducing measurement noise in the calculated result.Furthermore, one or the other of the combined values can be optionallycorrected with the relative sensitivity matching value S in step 380 andthe result can be optionally combined with the other value in step 390to provide an improved calculated value with reduced noise and greaterconfidence.

Alternatively, or in addition, the measurements, or combinedmeasurements of the second magnetic sensor B can be converted (e.g., asin step 200) and combined with the measurements, or combinedmeasurements, of the first magnetic sensor A, or vice versa as desired,for example as illustrated and discussed with respect to FIG. 8. Thus,the magnetic sensor controller 40 can compute or calculate the ambientmagnetic field excluding any field provided by the one or more inductors20 by computing a sum or difference or otherwise combining themeasurement by the first magnetic sensor A and the corrected measurementby the second magnetic sensor B.

Referring next to FIG. 10, in another embodiment of the presentinvention, the difference in spatial location between the first magneticsensor A and the second magnetic sensor B is exploited to measure theambient magnetic field gradient. As shown in FIG. 10, after the relativesensitivity matching value S is computed in step 160, the one or moreinductors 20 are optionally controlled by the magnetic sensor controller40 to provide a magnetic field, or not, in step 132. In either case, thecontrol circuit 42 controls the first magnetic sensor A to measure thethird ambient magnetic field A6 in step 400 and controls the secondmagnetic sensor B to measure the fourth ambient magnetic field B6 instep 410. In an embodiment, the measurements are performed at the sametime. One or the other of the measured third of fourth ambient magneticfields A6 or B6 is corrected using the relative sensitivity matchingvalue S in step 420. In step 430, the corrected measured value iscompared to or combined with the other measured value to calculate amagnetic field gradient by correcting one of the measured values andcombining the corrected value to the other measured value.

In general, the steps illustrated in FIGS. 6-10 can be repeated to makemultiple, sequential magnetic field measurements over time. The magneticsensor device 99 can be calibrated or otherwise adjusted betweenmeasurements or series of measurements, for example after periods of useor after a pre-determined number of uses.

If the current flow direction of the inductors 20 is alternated betweenmeasurements with a common current magnitude, the calibration can bedone at the time of a measurement. The difference between the twomeasurements with opposing field directions provides a calibration valuethat can be applied to the measurements. Moreover, when more than twoinductors 20 are present, any two of the inductors providing opposingfields can provide a calibration value and overlapping pairs ofinductors 20 can provide related calibration values, enabling thecalibration (matching) of more than two inductors 20 at a time.

Thus, in some embodiments of the present invention, the control circuitcontrols the first magnetic sensor A to measure a first magnetic fieldA1 and the one or more inductors to provide a fifth magnetic field,controls the first magnetic sensor A to measure a third magnetic fieldA2 and the one or more inductors to provide a seventh magnetic field,controls the second magnetic sensor B to measure a second magnetic fieldB1 and the one or more inductors to provide the sixth magnetic field,and controls the second magnetic sensor B to measure a fourth magneticfield B2 and the one or more inductors to provide the eighth magneticfield. In some embodiments, the fifth and/or sixth magnetic fields arezero, as described above. In other embodiments, the fifth and seventh,respectively sixth and eighth magnetic fields have opposite directionsor have a common magnitude so that the measurements are comparable.

In various embodiments of the present invention, more than theillustrated two first and second magnetic sensors A, B are included inthe magnetic sensor device 99, for example as shown in FIG. 5B. FIG. 5Billustrates an embodiment with three inductors 20 and threecorresponding common magnetic sensors A, B, C, all or any pair of whichcan be used for calculating the magnetic field. The sensitivity orresponse of each of the magnetic sensors 30 can be matched to a commonmagnetic sensor 30 with a possibly different relative sensitivitymatching value S corresponding to each of the other magnetic sensors 30.The sensitivity or response of each of the magnetic sensors 30 can thenbe corrected to be comparable to the common magnetic sensor 30 and theirmeasurements combined to provide improved or additional magnetic fieldvalues. For example, multiple measurements can provide a better estimateof the magnetic field gradient in a wider range of locations, forexample in a spatially linear series or in mutually orthogonal locationsto provide a two (or three) dimensional gradient measurement. In otherembodiments, multiple measurements can be combined to provide ameasurement with less noise, for example by averaging the multiplemeasurements or combinations of measurements or by finding multipledifferences of measurements.

In an embodiment of the present invention, the magnetic sensor device 99can be made by providing the substrate 10 and forming substrateconductors 16 and substrate contact pads 18 on the substrate 10,together with any necessary vias 17. In one configuration, the controlcircuit 42 is made on or in the substrate 10 using at least some of thesame processing steps or materials, for example using photolithographicand integrated circuit methods and materials. Alternatively, the controlcircuit 42, for example an integrated circuit, is micro-transfer printedto the substrate 10 or layers on the substrate 10, for example thedielectric layer 12. The magnetic sensor 30 can also be made on or inthe substrate 10 using at least some of the same processing steps ormaterials, for example using photolithographic and integrated circuitmethods and materials or can be micro-transfer printed to the substrate10 or layers on the substrate 10, for example the dielectric layer 12.Micro-transfer printed cores 22, magnetic sensors 30, or controlcircuits 42 enable a reduced form factor and improved functionality by,at least in part, dispensing with additional packaging.

If the magnetic sensor 30 or control circuit 42 are micro-transferprinted to the substrate 10 or layers on the substrate 10 (e.g.,dielectric layer 12) they can be electrically connected to the substrateconductors 16 as desired through vias 17 and substrate contact pads 18in any intervening layers (e.g., dielectric layer 12) as is commonlydone in the integrated circuit and printed circuit board arts.Alternatively, the control circuit 42 or magnetic sensor 30 are surfacemount devices and disposed using surface mount techniques. In anembodiment, the control circuit 42 is provided externally to thesubstrate 12 and electrically connected to the magnetic sensors 30 andone or more inductors 20 through wires, for example through a ribbon orflex cable.

The core(s) 22 can be provided, for example in a tape and reelconfiguration, as surface mount components, or as micro-transferprintable components and disposed over, on, or in direct contact withthe substrate 10 or layers on the substrate 10 such as dielectric layer12, for example using pick-and-place, surface mount, or micro-transferprinting. In one embodiment, the cores 22 are coated with an insulatorto form the core insulator 26 after disposition on the substrate 10, forexample by spray or spin coating, by evaporation, or by sputtering, andcured, if necessary. Alternatively, the entire inductor 20 or core 22and core insulator 26 is micro-transfer printed from a source wafer anddisposed on or over the substrate 10 or any layers on the substrate 10.In an embodiment, the coil electrical conductors 24 are formedlithographically over the core 22 structure and in contact with thesubstrate contact pads 18 by depositing and patterning an electricallyconductive material such as metal, as shown in FIG. 2B. In analternative embodiment of an inductor 20, FIG. 11, the coil electricalconductors 24 are provided by wire-bond wires from a first substratecontact pad 18 on one side of the core insulator 26, over the coreinsulator 26 to the other side of the core insulator 26, to a secondsubstrate contact pad 18, to form the helical coil 25. In thisembodiment, the wire-bonded wires are the coil electrical conductors 24.In an embodiment, if the electrical conductors 24 do not touch the core22, the core insulator 26 is not necessary.

Embodiments of the magnetic sensor device 99 of the present inventioncan be operated by providing electrical power to the control circuit 42,for example an electronic circuit. The electronic control circuit 42 cancontrol the magnetic sensors 30, the one or more inductors 20, or bothby providing signals to and receiving signals from the magnetic sensor30 and controlling the flow of electrical current through the one ormore inductors 20, for example individually, together, or in separategroups of inductors 20. In embodiments of the present invention, theelectronic control circuit 42 operates the magnetic sensor 30 to measurea magnetic field or to operate the one or more inductors 20 to provide atest magnetic field, or to operate the one or more inductors 20 tocalibrate the magnetic sensors 30, or any combination of thesefunctions. In an embodiment, the one or more inductors 20 provide amagnetic field at a magnetic sensor 30 location greater than or equal to1 mT, 3 mT, 5 mT, 10 mT, 15 mT, 20 mT, or 50 mT.

Methods of forming micro-transfer printable structures are described,for example, in the paper AMOLED Displays using Transfer-PrintedIntegrated Circuits (Journal of the Society for Information Display,2011, DOI #10.1889/JSID19.4.335, 1071-0922/11/1904-0335, pages 335-341)and U.S. Pat. No. 8,889,485, referenced above. For a discussion ofmicro-transfer printing techniques see, U.S. Pat. Nos. 8,722,458,7,622,367 and 8,506,867, each of which is hereby incorporated byreference in its entirety. Micro-transfer printing using compoundmicro-assembly structures and methods can also be used with the presentinvention, for example, as described in U.S. patent application Ser. No.14/822,868, filed Aug. 10, 2015, entitled Compound Micro-AssemblyStrategies and Devices, which is hereby incorporated by reference in itsentirety. In an embodiment, the magnetic sensor device 99 is a compoundmicro-assembled device. Additional details useful in understanding andperforming aspects of the present invention are described in U.S. patentapplication Ser. No. 14/743,981, filed Jun. 18, 2015, entitled MicroAssembled LED Displays and Lighting Elements, which is herebyincorporated by reference in its entirety.

As is understood by those skilled in the art, the terms “over”, “under”,“above”, “below”, “beneath”, and “on” are relative terms and can beinterchanged in reference to different orientations of the layers,elements, and substrates included in the present invention. For example,a first layer on a second layer, in some embodiments means a first layerdirectly on and in contact with a second layer. In other embodiments, afirst layer on a second layer can include another layer there between.Additionally, “on” can mean “on” or “in” or “over.”

Having described certain embodiments, it will now become apparent to oneof skill in the art that other embodiments incorporating the concepts ofthe disclosure may be used. Therefore, the invention should not belimited to the described embodiments, but rather should be limited onlyby the spirit and scope of the following claims.

Throughout the description, where apparatus and systems are described ashaving, including, or comprising specific components, or where processesand methods are described as having, including, or comprising specificsteps, it is contemplated that, additionally, there are apparatus, andsystems of the disclosed technology that consist essentially of, orconsist of, the recited components, and that there are processes andmethods according to the disclosed technology that consist essentiallyof, or consist of, the recited processing steps.

It should be understood that the order of steps or order for performingcertain action is immaterial so long as the disclosed technology remainsoperable. Moreover, two or more steps or actions in some circumstancescan be conducted simultaneously. The invention has been described indetail with particular reference to certain embodiments thereof, but itwill be understood that variations and modifications can be effectedwithin the spirit and scope of the invention.

1. A magnetic sensor device, comprising: a substrate having a surface; afirst magnetic sensor disposed at a first location on, over, or indirect contact with the surface, the first magnetic sensor beingconfigured for detecting a magnetic field; a second magnetic sensordisposed at a second location different from the first location on,over, or in direct contact with the surface, the second magnetic sensorbeing configured for detecting a magnetic field; one or more inductorsdisposed over the substrate surface and located to provide a magneticfield to the first magnetic sensor and to the second magnetic sensor;and a magnetic sensor controller having a control circuit forcontrolling the first magnetic sensor, the second magnetic sensor, andthe one or more inductors; wherein the control circuit includescircuitry adapted: for controlling the first magnetic sensor to measurea first magnetic field and the one or more inductors to provide a fifthmagnetic field; for controlling the first magnetic sensor to measure athird magnetic field and the one or more inductors to provide a sixthmagnetic field; for controlling the second magnetic sensor to measure asecond magnetic field and the one or more inductors to provide the fifthmagnetic field; for controlling the second magnetic sensor to measure afourth magnetic field and the one or more inductors to provide the sixthmagnetic field; for calculating a relative sensitivity matching valuethat converts magnetic field values measured by the first magneticsensor to a comparable magnetic field value measured by the secondmagnetic sensor or that converts magnetic field values measured by thesecond magnetic sensor to a comparable magnetic field value measured bythe first magnetic sensor.
 2. The magnetic sensor device of claim 1,wherein the inductor is a coil, a solenoid, or a straight conductor. 3.The magnetic sensor device of claim 1, wherein the fifth or the sixthmagnetic field is zero, or wherein the fifth and sixth magnetic fieldshave an opposite polarity, or wherein the fifth and sixth magneticfields have a common magnitude.
 4. The magnetic sensor device of claim1, wherein the control circuit includes circuitry adapted forcontrolling the first magnetic sensor to measure a first ambientmagnetic field, for controlling the second magnetic sensor to measure asecond ambient magnetic field, for correcting the ambient magnetic fieldmeasurement of the second magnetic sensor with the relative sensitivitymatching value to form a corrected measurement, and for combining theambient magnetic field measurement by the first magnetic sensor and thecorrected ambient magnetic field measurement to form a magnetic fieldmeasurement.
 5. The magnetic sensor device of claim 4, wherein thecontrol circuit includes circuitry adapted for controlling the firstmagnetic sensor to measure the ambient magnetic field at the same timethat the circuitry controls the second magnetic sensor to measure theambient magnetic field.
 6. The magnetic sensor device of claim 3,wherein the control circuit includes circuitry adapted for controllingthe one or more inductors to provide a magnetic field having a forwardpolarity and for controlling the first magnetic sensor to measure theambient magnetic field including the forward polarity magnetic field,for controlling the one or more inductors to provide a magnetic fieldhaving a reverse polarity and for controlling the first magnetic sensorto measure the ambient magnetic field including the reverse polaritymagnetic field, and for then calculating the ambient magnetic fieldexcluding any field provided by the one or more inductors by combiningthe two measurements.
 7. The magnetic sensor device of claim 1, whereinthe control circuit includes circuitry adapted for controlling the oneor more inductors to provide a magnetic field having a forward polarityand for controlling the first magnetic sensor to measure the ambientmagnetic field including the forward polarity magnetic field, forcontrolling the one or more inductors to provide a magnetic field havinga reverse polarity and for controlling the second magnetic sensor tomeasure the ambient magnetic field including the reverse polaritymagnetic field, for correcting the measurement by the second magneticsensor using the relative sensitivity matching value to produce acorrected measurement, and for then calculating the ambient magneticfield excluding any field provided by the one or more inductors bycombining the measurement by the first magnetic sensor and the correctedmeasurement.
 8. The magnetic sensor device of claim 1, wherein thecontrol circuit includes circuitry adapted for controlling the firstmagnetic sensor to measure the ambient magnetic field and forcontrolling the second magnetic sensor to measure the ambient magneticfield, for correcting the measurement by the second magnetic sensorusing the relative sensitivity matching value to produce a correctedmeasurement, and for calculating a magnetic field gradient by combiningthe measurement by the first magnetic sensor and the correctedmeasurement.
 9. The magnetic sensor device of claim 1, wherein therelative sensitivity matching value includes or is a multiplication ordivision factor, wherein the relative sensitivity matching valueincludes or is an additive or subtractive offset factor, or wherein therelative sensitivity matching value includes both a multiplication ordivision factor and an additive or subtractive offset factor.
 10. Amethod of matching multiple magnetic sensors in a magnetic sensordevice, comprising: providing a substrate having a surface, a firstmagnetic sensor disposed at a first location on, over, or in directcontact with the surface, a second magnetic sensor disposed at a secondlocation on, over, or in direct contact with the surface, the firstmagnetic sensor and the second magnetic sensor both being adapted fordetecting a magnetic field and the first location different from thesecond location, one or more inductors disposed over the substratesurface and located to provide a magnetic field to the first magneticsensor and to the second magnetic sensor; and controlling the firstmagnetic sensor to measure a first magnetic field and the one or moreinductors to provide a fifth magnetic field; controlling the firstmagnetic sensor to measure a third magnetic field and the one or moreinductors to provide a sixth magnetic field; controlling the secondmagnetic sensor to measure a second magnetic field and the one or moreinductors to provide the fifth magnetic field; controlling the secondmagnetic sensor to measure a fourth magnetic field and the one or moreinductors to provide the sixth magnetic field; and calculating arelative sensitivity matching value that converts magnetic field valuesmeasured by the first magnetic sensor to a comparable magnetic fieldvalue measured by the second magnetic sensor or that converts magneticfield values measured by the second magnetic sensor to a comparablemagnetic field value measured by the first magnetic sensor.
 11. Themethod of claim 10, comprising: controlling the first magnetic sensor tomeasure a first ambient magnetic field, controlling the second magneticsensor to measure a second ambient magnetic field, correcting theambient magnetic field measurement by the second magnetic sensor withthe relative sensitivity matching value to produce a corrected ambientmagnetic field measurement, and combining the corrected ambient magneticfield measurement and the ambient magnetic field measurement by thefirst magnetic sensor to form a magnetic field measurement.
 12. Themethod of claim 11, wherein measuring the first ambient magnetic fieldand measuring the second ambient magnetic field are carried out at thesame time.
 13. The method of claim 10, comprising: controlling the oneor more inductors to provide the fifth magnetic field having a forwardpolarity and controlling the first magnetic sensor to measure theambient magnetic field including the forward polarity magnetic field,controlling the one or more inductors to provide the sixth magneticfield having a reverse polarity and controlling the first magneticsensor to measure the ambient magnetic field including the reversepolarity magnetic field, and then calculating the ambient magnetic fieldexcluding any field provided by the one or more inductors by combiningthe two measurements.
 14. The method of claim 10, comprising:controlling the one or more inductors to provide the fifth magneticfield having a forward polarity and controlling the first magneticsensor to measure the ambient magnetic field including the forwardpolarity magnetic field, controlling the one or more inductors toprovide the sixth magnetic field having a reverse polarity andcontrolling the first magnetic sensor to measure the ambient magneticfield including the reverse polarity magnetic field, correcting themeasurement by the second magnetic sensor with the relative sensitivitymatching value to produce a corrected measurement, and then calculatingthe ambient magnetic field excluding any field provided by the one ormore inductors by combining the measurement by the first magnetic sensorand the corrected measurement.
 15. The method of claim 10, wherein therelative sensitivity matching value includes or is a multiplication ordivision factor, wherein the relative sensitivity matching valueincludes or is an additive or subtractive offset factor, or wherein therelative sensitivity matching value includes both a multiplication or adivision factor and an additive or subtractive offset factor.